Background

In patients who present to the Emergency Department (ED) with chest pain whose initial evaluation does not reveal acute myocardial infarction, the American Heart Association (AHA) recommends non-invasive testing to provoke ischemia or to detect coronary artery disease (CAD) before or within 72 hours of their discharge. Such testing is believed to identify patients who might benefit from more invasive therapy, such as coronary revascularization.

However, there is no evidence that non-invasive testing reduces the risk of future cardiac events compared with a more conservative approach. Multiple non-invasive testing options exist each with their own limitations in sensitivity, radiation exposures, and cost. Moreover, additional non-invasive testing may lead to increased invasive testing without accompanying benefit.

Clinical Question

What is the rate of downstream testing, intervention, and outcomes associated with chest pain evaluation strategies for patients in the ED?

Population

All adults presenting with chest pain to the ED whose initial evaluation for ischemia was without acute findings.

Intervention

Non-invasive testing within 7 days of presentation
(exercise electrocardiography (EE), myocardial perfusion scan (MPS), stress echocardiography (SE), CT coronary artery (CCTA))

Control

No additional testing within 7 days

Outcomes

Primary: The proportion of patients in each group who received a
cardiac catheterization, coronary revascularization procedure, or future noninvasive test at 7 and 190 days of follow-up.
Secondary: The proportion of patients in each group who were hospitalized for an acute myocardial infarction (MI) at 7 and 190 days of follow-up.

Design

Retrospective, observational study using health insurance claims data for a national sample of privately insured patients from January 1 to December 31, 2011.

Excluded

Patients who developed an MI or underwent cardiac catheterization, coronary revascularization, or CABG after ED presentation but before a noninvasive cardiac test was performed, did not maintain continuous insurance enrollment during the study period, received a primary or secondary diagnosis of respiratory, pulmonary vascular, pericardial, or aortic process associated with their chest pain.

Primary Results

Critical Findings

There were no significant differences in hospitalizations for MI between any of the non-invasive testing groups or relative to the no-testing cohort.

Subsequent Cardiac Catheterization

  • 12,608 patients (3%) and 22,388 patients (5.3%) received a cardiac catheterization at 7 and 190 days of follow-up.
  • Patients who underwent non-invasive testing had increased odds of receiving cardiac catheterization at 7 days relative to the no-testing cohort.
  • Adjusted Odds Ratios:
    • SE 1.10
    • EE 1.63
    • MPS 2.48
    • CCTA 1.91
  • Increased odds were seen at 190 days for all non-invasive strategies except SE.

Subsequent Revascularization

  • 3,078 patients (0.7%) and 5,668 patients (1.3%) underwent revascularization at 7 and 190 days of follow-up.
  • Patients who underwent non-invasive testing had increased odds of receiving coronary revascularization at 7 days relative to the no-testing cohort.
  • Adjusted Odds Ratios:
    • SE 1.54
    • EE 2.41
    • MPS 2.40
    • CCTA 3.56
  • Increased odds were seen at 190 days for all non-invasive strategies except SE.

Subsequent Non-invasive Cardiac Testing

  • 24,141 (5.7%) and 55,534 (13.2%) patients received a future non-invasive test at 7 and 190 days of follow-up.
  • Patients who underwent initial non-invasive imaging by 7 days follow-up had increased odds of receiving a future non-invasive test at 190 days relative to the no-testing cohort.
  • Adjusted Odds Ratios:
    • SE 1.47
    • EE 1.63
    • MPS 2.31
    • CCTA 1.58

 


  • 693,212 ED encounters with a primary or secondary diagnosis of chest pain (9.2% of all ED encounters) with 421,774 patients included in the final analysis.
  • 293,788 patients (69.7%) did not receive a non-invasive test within 7 days and 127,986 (30.3%) underwent testing.
  • MPS was the most frequently used modality (64.8%), followed by SE (18.8%), EE (14.2%), and CCTA (2.1%).
  • 464 patients (0.11%) and 1396 patients (0.33%)were hospitalized with an acute MI at 7 and 190 days of follow-up, respectively.

Strengths

  • Statistical adjustment for comorbidities
  • Valuable clinical question

Limitations

  • Retrospective, observational analysis reliant on ICD9 coding
  • No testing cohort was significantly younger and with less comorbidities that cannot all be adjusted for
  • No Medicare patients or < 65 years old
  • Mortality data unable to be captured

Author's Conclusions

“The low risk of MI did not appear to be affected by the initial testing strategy, and deferral of noninvasive testing appeared to be a reasonable approach...The significant increase in revascularization associated with MPS, CCTA, and EE without a concomitant reduction in MI suggests that overdiagnosis is a legitimate concern in this patient population.”

Our Conclusions

Low risk chest pain patients who undergo early non-invasive testing are more likely to undergo subsequent invasive cardiac testing. However, the use of non-invasive testing was not associated with improved MI rate at 7 or 190 days. Initial deferral of non-invasive testing may be a reasonable strategy.

Potential Impact To Current Practice

Although recommended by the AHA, early non-invasive testing may not be necessary in low risk chest pain patients as it may not improve outcomes. This could lead to a larger percentage of chest pain patients being discharged home from the ED after acute MI is ruled out.

Bottom Line

Patients who undergo early non-invasive testing after exclusion of acute myocardial infarction are more likely to subsequently undergo invasive cardiac testing without an improvement in outcomes.

Read More

Amsterdam EA et al. American Heart Association Exercise, Cardiac Rehabilitation, and Prevention Committee of the Council on Clinical Cardiology, Council on Cardiovascular Nursing, and Interdisciplinary Council on Quality of Care and Outcomes Research. Testing of low-risk patients presenting to the emergency department with chest pain: a scientific statement from the American Heart Association. Circulation. 2010;122(17):1756-1776. PMID: 20660809